WASHING AND GRADING SAND FOR CONCRETE. XI. 
set of experiments. All the figures need not be quoted, 
but the mixture finally adopted was 1 cement, 2 toppings, 
and 2 of 3-inch screenings. The crushing strain of this 
was 1053 tons per square foot at age of 50 days, as com- 
pared with 85 tons when using sand in lieu of toppings. 
The full mixture finally adopted was the above, with 3 parts 
of 2 inch bluestone. This gave acrushing strain of 99 tons 
per square foot. This is a splendid example of well graded 
materials forming a strong aggregate. 
Paper read before the Victorian Institute of Engineers, 
by CO. H. Oliver, c.z., October 2nd, 1889.’ 
Sand.—‘* The results are all the average of 5 briquettes, 
broken at 1 square inch, made with the same cement, and 
mixed in proportion of 1 part cement to 2 parts by measure 
of the sand to be tested, and broken at the age of 7 days. 
The full line on diagram shows the strength in Ibs. per sq. 
inch of the unwashed samples, whilst the dotted lines give 
that of the washed samples of the same sand. Nos. 1 to 
4 are Sandridge sands of different degrees of coarseness, 
No. 3 being much the coarsest. No. 5 to 7 are from the 
top of a hill near Kangaroo Ground. No. 6, you will 
observe, stood 170tbs. per square inch unwashed, and 
washed (some 36 per cent. being washed away) only stood 
87ibs. This sample was the first sand in which I found a 
result so at variance to the often expressed rule for sand 
for mortar or concrete, viz., ‘that the sand used must be 
clean, sharp and washed.’ Several sands from rivers and 
creeks gave the same results, though in general all river 
sands require washing, whilst hill sands do not. Nos. 8 to 
11 show examples of river sand. Five samples of crushed 
brick are next shown, No. 12 being a soft brick and No. 13 
very hard. Nos. 14 to 19 are river or creek sands, which 
seemed to the eye better than the hill sands 5 to 7. No. 
? Building and Engineering Journal, 12th October, 1889. 
